Oxidation of U(III) with Water in the Course of Precipitation of Its Solid Compounds from Aqueous Solutions

U(III) was precipitated from solution as a yellowish-brown precipitate under the action of NH4OH or Na2B4O7 solutions at pH similar to 7.5. The electronic spectra showed the presence of substantial amounts of U(OH)(3) in the precipitate, decreasing within a few minutes. Therefore, pure U(OH)(3) can hardly be obtained. A brown precipitate is formed when a U(III) solution is added to an NH4F solution. An X-ray phase analysis shows that anhydrous UF3 is the only crystalline compound in the precipitate. The synthesis of U(III) phosphate was unsuccessful, because uranium was completely oxidized to U(IV). Thus, preparation of U(III) phosphate compounds from aqueous solutions is hardly possible.